• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.5
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• pp.21-30
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• 2008

The fuel cell generation convert fuel source, and gas directly to electricity in an electro-chemical process. Unlike traditional and conventional turbine engines, the process of fuel cell generation do not burn the fuel and run pistons or shafts, and it has not revolutionary machine, so have fewer efficiency losses, low emissions and no noisy moving parts. A high power density allows fuel cells to be relatively compact source of electric power, beneficial in application with space constraints. In this system, the fuel cell itself is nearly small-sized by other components of the system such as the fuel reformer and power inverter. So, the fuel cell energy's stationary fuel cells produce reliable electrical power for commercial and industrial companies as well as utilities. In this paper, a fuel cell system has been modeled using PSCAD/EMTDC to analyze its electric signals and characteristics. Also the power quality of the fuel cell system has been evaluated and the problems which can be occurred during its operation have been studied by modeling it more detailed. Particularly, we have placed great importance on its power quality and signal characteristics when it is connected with a power grid.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.6
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• pp.456-464
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• 2007

This paper proposes a novel three-phase current-fed active clamp DC-DC converter for fuel cells. A single common active clamp branch is used to limit transient voltage across the three-phase full bridge and to realize zero-voltage switching(ZVS) in all switches. To apply for the power generation system current-fed type has been combined with the three-phase power conversion system. The proposed approach has the following advantages: an increase (by a factor of three) of input current and output voltage chopping frequencies; lower RMS current through the inverter switches with higher power transfer capability; reduction in size of reactive later components and the power conditioning system; better transformer utilization; increase of the system reliability. Therefore, the proposed three-phase current-fed active clamp DC-DC converter is appropriate for the boost type DC-DC converter for fuel cells and also applicable for the photovoltaic and battery charge system. The paper details the analysis, simulation and hardware implementation of the proposed system. Finally, experimental results with the proposed PWM strategy demonstrate the feasibility of the proposed scheme on a 500W prototype converter.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.6
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• pp.709-718
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• 2017

The installation of the elevator ARD(Automatic Rescue Device) system has been forced into law in these days in order to safely rescue passengers during power failure. The configuration of the ARD system consists of energy storage device, power converter and control systems. The EDLC(Electric Double Layer Capacitor) are used as energy storage device for rapid charge/discharge purposes. The power conditioning system (PCS) consists of bi-directional converter, 3-phase converter and control system. The dead-beat control system is adopted for most systems however it requires complex mathematical calculations, the high performance microprocessors are mandatory and thus it can be a cause of high manufacturing cost. In this paper the new control method for average current mode control is presented for simple structure. The control algorithm is applied to the single phase system and then expands to three phase system to meet the sysem requirements. The mathematical modeling using average modeling method is presented and analysed by PSIM computer simulation to verifie the validity of the proposed control methods.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.983-985
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• 2002

This paper is the machine that is able to estimate a new built power convertor in a production line. Generally, this machine test can be achieved by connecting it to a dynamometer consisting of a three-phase machine joined by a rigid shaft to a DC load machine. But the proposal system is controlled to create some specific load characteristic needed for the test without any mechanical equipment. The suggested test stand consists only of a converter to be test and a simulator converter. Both devices are connected back-to-back on the AC-side via smoothing reactors. The simulator operates in real-time as an equivalent load circuit, so that the device under test will only notice the behaviour of a three-phase machine under consideration of the load. And then, to obtain a superior characteristic for dynamic reference used the feedforward control.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1080-1084
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• 2011

Urban maglev should have such characteristics as not only environmentally friendliness and excellent driving capability but also curve negotiation performance because its routes have many sharp curves. Due to normal mechanism of urban maglev its relative displacements of secondary spring are bigger than conventional railway vehicle and the centering force of levitation magnet is smaller than wheel-on-rail system. These features of maglev affect the curving negotiation and so the additional steering device is to be required on Urban maglev to improve the running performance at sharp curve of less than about R50m. Some developed urban maglev had the passive steering device which consists of mechanical linkage or hydraulic cylinder and closed-route piping. But it has drawback as complexity of layout of understructure of vehicle and functional limitation of passive mechanism regarding transient curve. These demerits could be solved by using active steering system. But it has a weak point that an active device should have actuators and additional inverter or hydraulic power source. In this paper, the semi-active steering system for urban maglev is to be introduced.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.4
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• pp.476-483
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• 2014

This paper describes the operational analysis results of the bipolar DC distribution system coupled with the distributed generators. The energy management for AC/DC power trade and the operational principle of distributed generators and energy storages were first analyzed by computer simulation with PSCAD/EMTDC software. After then a hardware simulator for the bipolar DC distribution system was built, which is composed of the grid-tied three-level inverter, battery storage, super-capacitor storage, and the voltage balancer. Various experiments with the hardware simulator were carried out to verify the operation of bipolar DC distribution system. The developed simulator has an upper-level controller which operates in connection with the controllers for each distributed generator and the battery energy storage based on CAN communication. The developed hardware simulator are possible to use in designing the bipolar DC distribution system and analyzing its performance experimentally.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1645-1655
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• 2016

A Dynamic Voltage Restorer (DVR) model is proposed to eliminate the short-term voltage disturbances that occur in the grid-connected mode, the switching between grid-connected mode and the stand-alone mode of a Microgrid. The proposed DVR structure is based on a conventional cascaded H-bridge multilevel inverter (MLI) topology; a novel composite control strategy is presented, which could ensure the compensation ability of voltage sag by the DVR. Moreover, the compensation to specified order of harmonic is added to implement effects that zero-steady error compensation to harmonic voltage in specified order of the presented control strategy; utilizing wind turbines-batteries units as DC energy storage components in the Microgrid, the operation cost of the DVR is reduced. When the Microgrid operates under stand-alone mode, the DVR can operate on microsource mode, which could ease the power supply from the main grid (distribution network) and consequently be favorable for energy saving and emission reduction. Simulation results validate the robustness and effective of the proposed DVR system.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.355-356
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• 2016

기존 X-ray용 인버터의 경우, 일반적인 Full-bridge 인버터를 사용하여 낮은 효율이 발생하기 때문에 1.6kW이상의 고전압 출력을 요구하는 X-ray를 사용할 수 없는 문제점이 있다. 본 논문은 X-ray 구동용 인버터의 높은 출력이 가능한 고전압 출력용 ZVS Phase-Shift Full Bridge 인버터를 제안한다. 기존의 X-ray 구동용 인버터를 사용할 경우에는 낮은 효율 및 높은 출력 전압을 발생 시킬 수 없기 때문에 X-ray 발생이 어려우며, 높은 출력을 발생시키기 위해서는 회로의 전체적인 부피가 커지고 제작단가가 증가하는 단점이 있다. 반면 제안된 회로는 X-ray 구동용 ZVS Phase-Shift Full Bridge 인버터로써, 영전압 스위칭을 통해 높은 효율로 인버터 구동이 가능하고, 높은 출력 전압을 발생 시킬 수 있기 때문에 회로의 소형화 및 고출력 X-ray 발생이 가능한 장점을 갖는다. 본 논문에서는 제안된 회로의 이론적인 특성을 분석하고 모의실험을 통해 확인하였으며, 1.6kW급 X-ray 구동 인버터 회로에 적용하여 실험을 통해 우수성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.113-114
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• 2016

영구자석형 동기전동기를 구동하는 인버터에서는 기본적으로 정현파 운전 방식을 사용하지만 최근에는 구형파 운전 방식도 종종 사용되고 있다. 정현파 운전 방식은 구형파 운전 방식에 비해 토크 리플이 작고 기동 성능이 우수하며, 약자속 제어를 이용하여 정격 속도 이상의 고속 운전이 가능하다. 이에 비해 구형파 운전 방식은 제어 알고리즘이 간단하고 스위칭 손실이 적은 장점이 있지만, 토크 리플이 크고 정격 속도 이하의 영역에서만 운전이 가능하다는 단점이 있다. 최근에 인버터의 운전 중에 각각의 장점이 있는 이들 2가지 운전 방식을 서로 전환하는 방법으로 가전제품의 압축기와 같은 연속 부하에 적용하기 위한 연구가 진행되었다. 저속 구간에서는 스위칭 손실을 줄이기 위하여 구형파 운전 방식을 주로 사용하고, 고속 구간에서는 안정적인 제어 성능을 위하여 정현파 운전 방식을 사용한다. 또한, 이 2가지 운전 방식의 전환 구간에서의 발생되는 과도 상태를 짧게 줄이기 위하여 속도 및 전류 제어기의 제어 변수에 대한 초기화 방법이 제시되었다. 본 논문에서는 구형파 운전 구간의 속도 제어기에 비례 적분 전류 제어기를 추가하여 전류 리플을 감소시키고, 전환 구간에서의 속도 및 전류 제어기의 제어 변수에 대한 초기화 방법을 제시하였다.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.271-272
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• 2016

본 논문에서는 ESS 구성을 위한 고효율 3-레벨 양방향 인버터를 제안한다. 제안된 인버터는 저주파 레그와 고주파 레그로 구성되어, dc-link 전압과 계통간의 양방향 전력 변환을 수행한다. 제안된 인버터는 3-레벨의 전압을 제공하며 기존 풀브리지 타입의 2-레벨 인버터에 비해 고조파 성분이 적고 필터의 크기를 줄일 수 있다. 또한, 소자들에 걸리는 전압 스트레스가 낮고 동작 중에 스위칭 소자의 바디 다이오드를 사용하지 않기 때문에 도통 손실과 스위칭 손실을 최소화 할 수 있다. 따라서 제안하는 양방향 인버터는 기존 2-레벨 인버터 대비 높은 계통 전류 품질과 높은 효율을 제공한다. 최종적으로 시제품을 제작하여 제안하는 양방향 인버터의 타당성을 검증하였다.